Dealing with Other Folks’ Code and Phantom Fixes
Today I've spent far more time than I'd like to have on a problem that has seemed to plague me for months. There's a perl client app to my market data server and it is run to get end-of-day prices for a variety of instruments that we don't get (easily) any other way. Seems reasonable.
Oh, how I wish it were...
I've been hearing that it's working, and then it's not. I look into the data, and it's fine. Then it's not. I don't want to take over this application because it's something that the guys should be able to deal with, but it has been getting closer and closer to that point because I keep thinking it's clear, and then there's an issue.
Just yesterday, I had an issue with a wild bug in the market data server. I deployed it and all looked OK. Then today it's broken again. I'm not sure exactly why this is happening, but I wasn't going to take any unnecessary chances: get the latest driver libraries, and make it from scratch. Maybe there's a header file/library mismatch? Who knows, but I was getting tired of this.
I also got their perl application - including the data, and stripped it down to the point that it's getting the data, testing it, logging failures, and then skipping the updating of the database. I've run this and it's returned good data for everything - save the ones where the ticker is bad, or there's not sufficient data in the database to generate a good ticker.
At this point, I'm convinced that the market data server is OK, and the perl interface into it is also OK. The application should run without problem, but if it picks up another mysterious problem, I'm going to be looking at the machine it runs on to see if there's any problems. It's got to be something, and the code just isn't it.
Digging into other people's code and not re-writing it is one of the less fun things I have to do from time to time. It's like a tacit approval of the horrible way they have put together this application. It was (and is) a mess, and should be recoded to be a lot more streamlined and efficient, but that's not my call. Thankfully, for now, it's working. We'll see what tomorrow brings.